Hippocampal volume and treatment outcome in postpartum depression: Naturalistic data from a psychiatric parent-baby unit

Abstract

Background: Postpartum depression (PPD) is a highly prevalent postpartum complication, impairing maternal quality of life, mother-infant bonding, and child development. While smaller hippocampal volume is reliably associated with worse treatment outcome in major depressive disorder (MDD), studies investigating associations between hippocampal volume and treatment outcome in PPD remain scarce.

Methods: In this naturalistic study, we analyzed T1-weighted MRI scans and behavioral data from mothers diagnosed with PPD, admitted for in-patient treatment at a psychiatric parent-baby unit between January 1, 2021, and December 1, 2023. Separate logistic and linear regression models were fitted for each left and right hippocampal volume as predictor of treatment outcome defined as treatment response (≥50 % reduction in MADRS score or discharge MADRS ≤10) and overall symptom reduction (percentage change in MADRS score from admission to discharge).

Results: The final sample included 18 participants (mean age 31.50 years, SD = 4.78). Right hippocampal volume was significantly associated with overall symptom reduction (β = -0.5, F(1, 16) = 5.29, p = .035, R² = 0.2486).

Conclusion: Our findings offer novel insights, highlighting an association between reduced hippocampal volume and improved treatment outcome in PPD. Widespread cortical grey matter reductions across the peripartum period have been linked to enhanced mother-infant bonding and may hence play a beneficial role in the therapeutic trajectory of PPD. Contrasting patterns typically observed in MDD, this inverse relationship further underlines distinct neurobiological features of PPD.

Keywords: Biomarker; MRI; Postpartum depression; Treatment outcome; hippocampus.